1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to transmitting and receiving data using multicasting, and more particularly, to performing Internet Protocol (IP) communication using multicasting by transmitting and receiving a packet containing IP information between a server and a client that do not know IP information about the other party.
2. Description of the Related Art
There are three types of IP addresses: unicast, broadcast, and multicast.
For a host on a shared network such as Ethernet, each Ethernet frame contains source and destination Ethernet addresses. Each Ethernet frame is typically sent to a single host and a destination address specifies a single interface.
Unicasting such as Ping, Telnet, FTP, and WWW is communication between a single sender and a single receiver.
A host may send a frame to all hosts on a network, which is called broadcasting.
Broadcasting used to send only one data to multiple clients is more efficient than unicasting in terms of line usage but cannot provide reliable delivery of data.
Multicasting stands in the middle of the scale of “unicast-multicast-broadcast” and is used to send each frame to a selected group of receivers on a network.
Multicasting is an efficient way of delivering one-to-many or many-to-many communications and uses a multicast group address to send a continuous data stream.
The drawback of broadcasting is that even a host which is not related to the broadcast frame must process the received frame.
On the other hand, a multicast method prevents an unnecessary packet from being delivered to the other hosts as would be the case in a broadcast method, because source data is duplicated and routed to a client.
Multicasting is used to reduce the load of a non-related host, and a host is a member of one or more multicast groups.
FIG. 1 is a conceptual diagram showing conventional unicast, broadcast, and multicast models.
Referring to FIG. 1, in the unicast model, a sender transmits data to a receiver on the same or different network. To transmit the same data to multiple receivers, the sender must reproduce the same number of copies of data as the number of receivers, thus leading to increased network load.
In the broadcast model, a sender can transmit data to multiple receivers on the same network using a single copy of data.
In the multicast model, a sender may transmit data to multiple receivers on the same or different network. The duplication amount of data varies depending on the logical position of receivers.
An IP may be installed on a personal computer (PC) either manually or automatically.
To install IP manually, a user asks a network administrator for basic information and directly inputs the information such as an IP address, a default gateway, a subnet mask, and a domain name server (DNS) assigned to a PC. In this case, the IP address, typically called a static IP address, is used for a PC to access the Internet.
To install IP automatically, Dynamic Host Configuration Protocol (DHCP) is used. That is, a DHCP server automatically assigns an IP address, a default gateway, a subnet mask, and a DNS.
The IP address is assigned by the DHCP server through search, proposal, request, and authentication.
When a PC boots up, it requests allocation of IP from a DHCP server and the DHCP server assigns one of its own IP addresses to the PC. The IP address automatically assigned to the PC can change each time the PC boots. This is called a dynamic IP address.
In general, unicasting is used for data communication between PCs. A sending PC must know the IP address and Port number of a receiving PC which vary depending on the type of a transmission protocol such as Hyper Text Transfer Protocol (HTTP), File Transport Protocol (FTP), or Telnet in order to send a data packet using unicasting.
The data packet contains IP information (IP addresses and port numbers) regarding the sending PC and the receiving PC. When IP information regarding the receiving PC is changed, the sending PC modifies IP information regarding the receiving PC contained in the data packet for transmission.
FIG. 2 is a conceptual diagram of conventional IP communication.
A header in a data packet transmitted from a sender to a receiver contains IP address and port number of the sender which vary depending on a transmission protocol and IP address and port number of the receiver.
The sender sends the data packet to the receiver through a routing path and the receiver then sends an acknowledgement (ACK) back to the sender.
To receive data from a server in a client-server network architecture, the client must be aware of the IP information of the server. When the server has a dynamic IP address, the address of the server contained in a sending data packet needs to be modified for transmission each time the address changes. Therefore, an apparatus and method are needed which transmits and receives a packet containing IP information.